Tides and Storms

Energy flows from the tropics to the poles. The tropics absorb most of the sun’s radiation and drives heat flow to polar regions where radiative cooling dominates. In winter the Hadley cell moves heat to ~30N via huge convective currents transporting latent heat from the tropics northwards via a band of powerful thunderstorms . The reverse happens in the northern summer when the tropical Hadley cell moves southwards towards the now winter southern hemisphere and it reverses circulation. David Randall explains this well in his book ‘Atmosphere, Clouds and Climate’ (from which the first 3 figures below are taken).

The rising branch of tropical thunderstorms (ITCZ) is located about 10 deg from the equator in whichever is the summer hemisphere. The release of latent heat warms the troposphere to the moist adiabatic lapse rate. The high warm air moves meridionally and cools by radiating heat, so becoming more dense. It then descends and twists eastward due to the rapidly increasing coriolis forces with latitude. A counter rotating Ferrel cell is driven by the mechanical energy of storms 60 -30 deg and balance mass flow. The JET stream is caused by the coriolis force acting on the descending Hadley circulation accelerated by zonal wind effects. It is concentrated about 12 km up due to lapse rate temperature gradients. The coriolis component of angular momentum M for the earth rotating with angular velocity at latitude and zonal wind u is:

u = 0 at the equator wheras u = 11m/s at 30N

The Jet stream strengthens as the polar night begins. This is closely related to winter storms as the temperature gradient between the tropics and the winter pole increases. This “thermal wind” in mid latitudes is caused by horizontal temperature gradients which increase strongly in winter. Hydrostatic balance vertically becomes unstable

The natural 60 year heat cycle recently observed in the Atlantic implies that the underlying trend of anthropogenic warming since 1942 has been only ~0.45C. This value results in a derived transient climate response (TCR) of ~1.5C. The conclusions of the AR5 attribution study now look questionable because they ignore any natural warming component post 1970.

Figure 10.5 in the AR5 attribution chapter is based on model comparisons from 1951 to 2010 is now looking rather unlikely because this result leaves no room for any natural component to warming, as shown below.

The new evidence of a significant oceanic warming and cooling cycle means that between 1950 and 2010 anything up to 50% of the rise in observed temperature was actually due to the warming phase of the 60y cycle. The error bars on the ‘ANT’ component in figure 10.5 are just too small to allow for this. If this is the case how can we best estimate the underlying anthropogenic component?

The true anthropogenic component of warming can be identified by subtracting off the natural warming/cooling cycle. The peaks of the oscillation occur both in 1942 and 2008 so the rise in temperature between these two dates should measure the underlying human induced CO2 warming.............................................>>

At http://tallbloke.wordpress.com/2014/02/23/jaime-jessop-climate-wars-co2-... ... where it seems lunar tides may have affection the Great Storm of 1703. Meanwhile, at www.spaceweather.com August 4th thee is a big sun spot lined up and facing the Earth. Mostly, people commenting are a trifle sceptical of the Corbyn forecast - but time will tell. It is accepted, however, that lunar tides influence the jet stream and this is all part of Corbyn's prediction methodology (both solar and lunar). Bob Weber is adamant that Corbyn is often right. He makes the point that from August 8th the Moon will be heading north until the 20th - 'and it will bring warm humid tropical air with it, no matter what the Sun is doing ...' and 'the Moon's influence through tidal action on the northern hemisphere atmospheric temperature will, by August 20th, exactly compliment the Sun's less active face. The fact that it is a super moon this month will intensify such tidal effects. The Moon's atmospheric tides act as a mixer of warm tropical air and cold polar air by jet stream movements ...'.

Clive Best (see link above) claims gravitational tides influence the flow of the polar jet stream and can therefore change the weather patterns at high latitudes. This coming supermoon will be the third one this year, 2014. Meanders in the jet stream caused cold weather in NE America and the UK became the target for transatlantic storms. In anothe post at http://clivebest.com/blog/?p=5937 ... he has another post on the Moon and how it affects the jet stream. Roberto Madrigali, an Italian meteorologist, said varyingt tidal forces during the lunar cycles change the position of the meanders (or Rosby Waves) in the polar jet stream. He has also written a book on the subject.

Another factor to bear in mind is the speed of the jet stream - it is not consistent and can double the rate of knots.

The fiercest storms to hit the UK last winter were two successive depressions between January 3rd and January 6th. The first storm brought flooding to Dorset, Aberystwyth and Northern Ireland. The second storm seems to have spawned off the first and produced the highest winds and rainfall. The coastline from Cornwall to Ireland was hit on January 6th by 8m waves and a storm surge. Again strong tides seem to have played a significant role.

The first storm swept through on the 3rd January, after doubling in size as the Jet Stream dipped downwards on the 2nd January. This was a period of exceptional tides.>>>>>>

This post will present evidence that strong tides were a primary cause of the December 5/6 storm that surged down the North Sea last winter. The first observation to be noted s the remarkable coincidence that all of the UK December storms coincided with maxima in tidal forces, as shown below.

So now let’s look in detail at the first of these – 5/6 December storm. This first December storm also had the strongest tides of the year. The Met office writes the following description:

The first storm of 5 December brought very strong winds to Scotland and northern England, and a major storm surge affecting North Sea coasts. A week of quieter weather then followed, but from mid-December there was a succession of further major winter storms which continued into early January.

On the 3rd December a low depression system had already just passed north of the UK and appeared to be weakening. However for some reason it stalled and then strengthened on the 4th and 5th December while it descended south along the east coast of the UK. The associated storm surge caused extensive coastal flooding. This storm was very similar to the devastating 1953 storm which killed 300 people in the UK and over a thousand in the Netherlands. This experience led to the strengthening of coastal defenses and the eventual construction of the Thames barrage. This 1953 storm also coincided with a high spring tide and extensive storm surge.

I aim to demonstrate in this series of posts that ever changing gravitational tides influence the flow of the polar Jet Stream thereby changing weather patterns at high latitudes. Such effects should be included in global circulation models to improve medium range weather forecasting.

Previously I described a proposal from Roberto Madrigali that tides acting on the Jet Stream affect high latitude weather (North and South). Robert Currie and others have reported long term coincidences of drought with Lunar Cycles (1). H. Yndestad reports lunar cycles in Arctic climates (2) and Li & Zong have reported lunar induced variations in global wind speed (3). Over 3000 years of folklore also links the moon to extreme weather on earth. Is all this just nonsense, or could atmospheric tides really be responsible for much of our weather in Europe and North America?

I decided to look into this in more detail and have spent the last few days calculating the horizontal tidal forces acting on the earth. To do this I used the JPL ephemeris to calculate the net tidal vector of the moon and the sun acting on the earth, and used the formulae derived previously to determine the horizontal tractional force for a given angular separation from the central net vector. In a north south direction this angular separation is the same as latitude. It is these tractional forces that cause the ocean currents that generate the two familiar tidal bulges. Although the forces are about 10 million times smaller than gravity they act perpendicular to gravity and cover vast regions of the earth. They also generate measurable winds in the upper atmosphere especially near the poles. The largest tractional forces occur at the extremes of latitude and can vary dramatically from month to month and year to year as the relative positions of the earth moon and sun change. The rotation of the earth then causes the familiar ~twice daily high tides. Their effect on the atmosphere is yet more complex also generating a small torque through the Coriolis effect.................